The mechanism of generalized genetic recombination carried out by the bacteriophage P22 essential recombination function (erf gene) will be studied by biochemical and genetic means. The erf gene and, possibly, other P22 recombination genes will be placed in a plasmid cloning vehicle. Plasmids that express the cloned erf gene will be constructed by in vitro genetic engineering methods. These plasmids will be placed in host cells carrying mutations in recombination genes, and tested genetically for suppression of the host cell defects by the phage recombination genes. Plasmids that express the cloned genes at high levels will be constructed and exploited for purification of P22 recombination proteins. The purified proteins will be tested for enzymatic activities related to recombination, and for function in actual recombination in vitro. The long-term goal of this research is an understanding of the mechanisms of genetic recombination. Recombination is a process of fundamental importance in the generation of genetic variation and, in higher organisms, of diversity in the immune response.